since when was this valid syntax?

[Maxim Fomin]

2012/9/8 Timon Gehr <timon.gehr at gmx.ch>:
> On 09/08/2012 09:25 PM, Maxim Fomin wrote:
>>
>> On Saturday, 8 September 2012 at 16:00:44 UTC, Timon Gehr wrote:
>>>
>>> On 09/08/2012 04:11 PM, Ellery Newcomer wrote:
>>>>
>>>> alias enum int e;
>>>
>>>
>>> It is valid according to the grammar and DMD ignores meaningless
>>> attributes.
>>>
>>> scope shared @disable @trusted package final override deprecated
>>> extern __gshared synchronized pure nothrow ref static abstract
>>> immutable alias auto final override deprecated extern __gshared
>>> synchronized enum pure nothrow ref static abstract @safe @disable
>>> scope int e;
>>
>>
>> How dmd's parser is written if it allows such things?
>
>
> It's the grammar that allows this. Every parser that follows the grammar
> would accept this.

Where is this grammar been defined? It looks more like a bug.